Isotopically-enriched boron-containing compounds, and methods of making and using same

ABSTRACT

An isotopically-enriched, boron-containing compound comprising two or more boron atoms and at least one fluorine atom, wherein at least one of the boron atoms contains a desired isotope of boron in a concentration or ratio greater than a natural abundance concentration or ratio thereof. The compound may have a chemical formula of B 2 F 4 . Synthesis methods for such compounds, and ion implantation methods using such compounds, are described, as well as storage and dispensing vessels in which the isotopically-enriched, boron-containing compound is advantageously contained for subsequent dispensing use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation in part under 35 USC 120 of U.S. patentapplication Ser. No. 12/913,721 filed Oct. 27, 2010, which in turnclaims the benefit of priority under 35 USC 119(e) of the following U.S.Provisional Patent Applications: U.S. Provisional Patent Application No.61/378,353 filed Aug. 30, 2010 in the names of Oleg Byl, et al. for“ISOTOPICALLY-ENRICHED BORON-CONTAINING COMPOUNDS, AND METHODS OF MAKINGAND USING SAME;” U.S. Provisional Patent Application No. 61/375,031filed Aug. 18, 2010 in the names of Oleg Byl, et. al. for“ISOTOPICALLY-ENRICHED BORON-CONTAINING COMPOUNDS, AND METHODS OF MAKINGAND USING SAME;” U.S. Provisional Patent Application No. 61/358,514filed Jun. 25, 2010 in the names of Edward Jones, et al. for “ACTIVECOOLING FOR ION IMPLANT GAS DELIVERY SYSTEM;” U.S. Provisional PatentApplication No. 61/349,202 filed May 27, 2010 in the names of EdwardJones, et al. for “ACTIVE COOLING FOR ION IMPLANT GAS DELIVERY SYSTEM;”and U.S. Provisional Patent Application No. 61/255,097 filed Oct. 27,2009 in the names of Robert Kaim, et al. for “BORON ION IMPLANTATIONAPPARATUS AND METHOD.” The disclosures of all of said U.S. patentapplication Ser. No. 12/913,721 and U.S. Provisional Patent ApplicationNos. 61/378,353; 61/375,031; 61/358,514; 61/349,202; and 61/255,097 arehereby incorporated herein by reference, in their respective entireties,for all purposes.

FIELD

The present disclosure relates to isotopically-enriched boron-containingcompounds, compositions, and methods of making and using same.

DESCRIPTION OF THE RELATED ART

Ion implantation is used in integrated circuit fabrication to accuratelyintroduce controlled amounts of dopant impurities into semiconductorwafers and is a crucial process in microelectronic/semiconductormanufacturing.

In such implantation systems, an ion source ionizes a desired dopantelement of a dopant source gas. The ion source generates ions byintroducing electrons into a vacuum chamber filled with the dopantsource gas (also commonly referred to as the “feedstock gas”). Feedstockgases used to generate implant species include, but are not limited to,BF₃, B₁₀H₁₄, B₁₂H₂₂, PH₃, AsH₃, PF₅, AsF₅, H₂Se, N₂, Ar, GeF₄, SiF₄, O₂,H₂, and GeH₄. The compositions containing the dopant element to beimplanted are typically referred to as dopant sources or precursors.Collisions of the electrons with dopant atoms and molecules in the gasresults in the creation of an ionized plasma consisting of positive andnegative dopant ions.

The resulting ions are extracted from the source in the form of an ionbeam of desired energy. Extraction is achieved by applying a highvoltage across suitably shaped extraction electrodes, which incorporateapertures for passage of the extracted beam. The extracted beam passesthrough the aperture and out of the ion source as a collimated ion beam,which is accelerated towards the substrate.

The ion beam is impinged on the surface of the substrate, such as asemiconductor wafer, in order to implant the substrate with the dopantelement. The ions of the beam penetrate the surface of the substrate toform a region of desired conductivity. Implanted ion species variouslyinclude B, P, As, Se, N, Ar, Ge, Si, O, and H, with boron being aparticularly widely used implant species.

One of the main steps in manufacturing of integrated circuits isimplantation of boron into silicon wafers. Since elemental boronexhibits very low vapor pressure even at high temperatures, utilizationof volatile boron-containing compounds is necessary. Currently, borontrifluoride (BF₃) is widely used as a feed gas for boron implantation(for example, it is estimated that the 2007 annual worldwide consumptionof BF₃ for ion implantation was ˜3000 kg).

Despite its widespread use, BF₃ does have disadvantages. The BF₃molecule is very difficult to ionize and only about 15% of all BF₃flowed into the ion source can be fragmented. The rest is discarded.Further, only about 30% of the ionized BF₃ is converted into B⁺ ionsthat can be used for implantation. This results in low B⁺ beam currentthat severely limits implantation process throughput.

Some increase of B⁺ beam current can be achieved by varying the processparameters, such as by raising the extraction current, and by increasingthe BF₃ flow rate. These measures result in reduced life time of the ionsource, high voltage arcing leading to tool instability, and poor vacuumcausing beam energy contamination. Even without drastic adjustment ofthe implantation process parameters, it is well established thatimplantation of boron requires more frequent preventive maintenanceinterruptions that present other problems for integrated circuitmanufacturers.

The problem of throughput limitation because of low B⁺ beam current hasbecome more important in recent years due to the semiconductorindustry's general trend toward utilization of lower implantationenergies. At lower implantation energies, the B⁺ beam experiences agreater blow-out effect due to space charge and the low atomic weight ofboron.

In addition to the foregoing problems, it has been mentioned thatelemental boron has a very low vapor pressure. Accordingly, if aboron-containing precursor is susceptible to excessive decompositionresulting in deposition of boron residue, then it may be unsuitable forion implantation, from an ion implanter tool operation perspective.

In consequence of the foregoing, the art continues to seek improvedboron precursors.

SUMMARY

The present disclosure relates to isotopically-enriched boron-containingcompounds, and methods of making and using same.

In one aspect, the disclosure relates to an isotopically-enriched,boron-containing compound comprising two or more boron atoms and atleast one fluorine atom, wherein at least one of the boron atomscontains a desired isotope of boron in a concentration or ratio greaterthan a natural abundance concentration or ratio thereof.

A further aspect of the disclosure relates to a method of implantingboron into a substrate, comprising ionizing the compound of anabove-describe type, to generate boron ions; and implanting the boronions into a substrate.

Yet another aspect of the disclosure relates to a beam-line ionimplantation, plasma immersion ion implantation or plasma doping system,comprising a source of the compound described above.

Another aspect of the disclosure relates to a gas storage and dispensingvessel comprising a compound of a above-described type.

The disclosure in another aspect relates to a method of improving beamcurrent for an ion implantation process, comprising: flowing thecompound of a type as described above; and generating an ion beam fromthe compound.

A further aspect of the disclosure relates to a method of synthesizingthe compound of a type as described above, comprising contacting aboron-containing gas with a boron metal.

The disclosure relates another aspect to a method of preparing a sourceof the compound of an above described type, comprising filling a storageand dispensing vessel with the compound.

Another aspect of the disclosure relates to an ion implantation method,comprising flowing a compound of the type described above to an ionimplantation tool with at least one co-flowed species selected from thegroup consisting of inert gas, argon, nitrogen, helium, hydrogen,ammonia, xenon, xenon difluoride, isotopically enriched diborane, andnatural abundance diborane.

A further aspect of the disclosure relates to an ion implantationmethod, comprising flowing an isotopically-enriched atomic mass 11 boronB₂F₄ compound to an ion implantation tool with an isotopically-enrichedatomic mass 11 boron BF₃ compound.

Yet another aspect of the disclosure relates to an ion implantationmethod comprising use of a compound of an above-described type in an ionimplantation tool, and periodically cleaning said tool or a componentthereof by flow therethrough of a cleaning agent that is effective to atleast partially remove deposits formed in said tool or a componentthereof by ion implantation operation.

A further aspect of the disclosure relates to a method of carrying oution implantation, comprising using a compound of a type as describedabove in an ion implantation tool as the only dopant source compoundused in operation of said ion implantation tool.

Another aspect of the disclosure relates to a method of carrying out ionimplantation, comprising conducting said ion implantation in an ionimplantation tool processing only isotopically enriched atomic mass 11boron B₂F₄ as a dopant compound therein.

In another aspect, the disclosure relates to a method of carrying oution implantation, comprising conducting said ion implantation in an ionimplantation tool using isotopically enriched atomic mass 11 boron B₂F₄as a dopant compound therein, wherein the ion implantation tool alsoprocesses at least one of arsine, phosphine, carbon dioxide, carbonmonoxide, silicon tetrafluoride and boron trifluoride.

A further aspect of the disclosure relates to a storage and dispensingvessel containing a compound of an above-described type in a storagemedium selected from the group consisting of physical adsorbents andionic liquids.

Yet another aspect of the disclosure relates to a storage and dispensingvessel containing a compound of an above-described type, wherein thevessel contains a restricted flow orifice located either within thevessel or within an output port of the vessel.

A further aspect the disclosure relates to a storage and dispensingvessel containing a compound of an above-described type, wherein thevessel is pressure-regulated for dispensing of the compound atsubatmospheric pressure.

The disclosure relates in another aspect to an ionized compositionuseful for AMU separation to generate ionic species for ionimplantation, said composition deriving from a boron precursor compoundother than BF₃, wherein said boron precursor compound is isotopicallyenriched beyond natural abundance in one of ¹⁰B and ¹¹B, and whereinsaid composition comprises one or more species from among B₂F₄ ⁺, B₂F₃⁺, B₂F₂ ⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, F⁺, B₂F₄ ⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺,BF₂ ⁺⁺, BF⁺⁺, B⁺⁺, F⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺, B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺,BF⁺⁺⁺, B⁺⁺⁺, and F⁺⁺⁺, the boron-containing ones of which areisotopically enriched beyond natural abundance in one of ¹⁰B and ¹¹B.

A further aspect of the disclosure relates to a boron ionic speciesselected from among B₂F₄ ⁺, B₂F₃ ⁺, B₂F₂ ⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, B₂F₄⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺, BF₂ ⁺⁺, BF⁺⁺, B⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺,B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺, BF⁺⁺⁺ and B⁺⁺⁺, and isotopically enrichedbeyond natural abundance in one of ¹⁰B and ¹¹B.

The disclosure in another aspect relates to a method of improving beamcurrent for an ion implantation process, comprising use of anisotopically-enriched, boron-containing compound that is effective toform isotopically enriched ionic species producing such improved beamcurrent, in relation to a corresponding non-isotopically-enriched,boron-containing compound.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a semiconductor manufacturingfacility including an ion implantation system arranged to receive anisotopically-enriched boron-containing precursor from a precursor supplyvessel, according to one embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure relates to isotopically-enriched boron-containingcompounds, compositions, and to methods of making and using same.

In one aspect, the disclosure relates to an isotopically-enriched,boron-containing compound comprising two or more boron atoms and atleast one fluorine atom, wherein at least one of the boron atomscontains a desired isotope of boron in a concentration or ratio that isgreater than a natural abundance concentration or ratio thereof (of thedesired isotope).

The boron-containing compound can be of any suitable type, and caninclude any number of boron atoms. In one embodiment, theboron-containing compound contains at least two boron atoms and at leastone fluorine atom. In another embodiment, the boron-containing compoundcontains from 2 to 80 boron atoms, including diboron compounds such asB₂F₄, B₂H₆, H₂B₂F₆, H₂B₂F₂O₃, H₂B₂F₂O₆, and H₂B₂F₄O₂, triboron compoundssuch as B₃F₆, tetraboron compounds such as H₄B₄F₁₀, B(BF₂)₃CO₃ and(F₂B)₃BCO, pentaboron compounds, hexaboron compounds, septaboroncompounds, octaboron compounds such as B₈F₁₂, nonaborane compounds,decaboron compounds such as B₁₀F₁₂, undecaboron compounds, dodecaboroncompounds, etc., up to B₈₀ compounds such as B₈₀ analogs of fullerenes.In other embodiments, the boron-containing compound can contain 2, 3, 4,5, 6, 7, 8, 9, 10, or 11 boron atoms. Additional embodiments maycomprise cluster boron compounds. In still other embodiments, theboron-containing compound can be a diboron compound. In otherembodiments, the boron-containing compound can comprise diboroncompounds other than particular boron-containing compound species, e.g.,diboron compounds other than diborane. It will therefore be appreciatedthat the disclosure contemplates a wide variety of classes ofboron-containing compounds, within the broad scope thereof.

In one embodiment of the isotopically-enriched, boron-containingcompound, the desired isotope is atomic mass 10 boron and the naturalabundance concentration is about 19.9%. In such boron compound, theconcentration of atomic mass 10 boron isotope can for example be greaterthan 19.9%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%,85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.9%, or 99.99%, in specificcompositional variants. For example, the concentration of atomic mass 10boron isotope can be 20-25%, 25-30%, 30-35%, 35-40%, 40-45%, 45-50%,50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95%,95-99% or 95-99.9%. In other embodiments, the concentration of atomicmass 10 boron isotope can be 20-30%, 30-40%, 40-50%, 50-60%, 60-70%,70-80%, 80-90%, or 90-99%. In various ones of these various embodiments,the boron-containing compound contains two boron atoms.

In another embodiment of the isotopically-enriched, boron-containingcompound, the desired isotope is atomic mass 11 boron and the naturalabundance concentration is about 80.1%. In such boron compound, theconcentration of atomic mass 11 boron isotope can for example be greaterthan 80.1%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.9% or 99.99%, inspecific compositional variants. For example, the concentration ofatomic mass 11 boron isotope can be 81-85%, 85-90%, 90-95%, 95-99%,95-99.9%. In a specific embodiment, the concentration of atomic mass 11boron isotope can be 81-90% or 90-99%. In various ones of these variousembodiments, the boron-containing compound contains two boron atoms andat least one fluorine atom, and in other compounds, the ratio of ¹¹B to¹⁰B is in a range of from 4.1 to 10,000.

In various embodiments of the isotopically-enriched boron-containingcompounds as described above, the boron-containing compound has achemical formula of B₂F₄. In various other embodiments of theisotopically-enriched boron-containing compounds as described above, theboron-containing compound has a chemical formula of B₂F₆.

More generally, in isotopically-enriched, boron-containing compounds ofthe present disclosure, the concentration of desired isotopes in the twoor more boron atoms can be the same as, or different from, one another.In various embodiments of the isotopically-enriched boron-containingcompounds of the present disclosure, the boron-containing compoundcontains 3, 4, 5, 6, 7, 8, 9, 10, or 11 boron atoms.

The present disclosure, in one aspect, relates to a method of implantingboron into a substrate, comprising ionizing an isotopically-enriched,boron-containing compound as variously described herein, to generateboron ions, and implanting the boron ions into a substrate. In suchmethod, the isotopically-enriched, boron-containing compound may be ofany suitable type described hereinabove. In one embodiment, the compoundhas a chemical formula of B₂F₄. In various other embodiments of suchmethod, the isotopically-enriched, boron-containing compound has achemical formula of B₂F₆.

The disclosure in another aspect relates to a beam-line ionimplantation, plasma immersion ion implantation or plasma doping system,comprising a source of the isotopically-enriched, boron-containingcompound, wherein the compound may be of any type as variously describedhereinabove. In one embodiment, the compound has a chemical formula ofB₂F₄. In various other embodiments of such method, theisotopically-enriched, boron-containing compound has a chemical formulaof B₂F₆. In another embodiment, the disclosure relates to ionimplantation, in which boron ions are generated and accelerated by anelectric field for impingement on a substrate, such as a microelectronicdevice substrate. Such method of implanting boron-containing ions in oneimplementation includes ionizing a boron-containing dopant species at ahigh ionization efficiency of at least 15% using an arc voltage lessthan 100 volts, preferably less than 90 volts, more preferably less than80 volts, and most preferably less than 70 volts, using a conventionalhot cathode ion source or comparable voltages using another ion source.In other embodiments, the ion implantation specifically excludes plasmaimmersion processes.

The above-described beam-line ion implantation, plasma immersion ionimplantation or plasma doping system, in specific implementationsthereof, comprise a conduit adapted for delivery of theisotopically-enriched boron-containing compound to an ionizationchamber, wherein the conduit is maintained at a temperature effective tominimize or otherwise suppress clogging of the conduit and/ordecomposition of the compound in the conduit. For such purpose, theionization chamber and/or the precursor feed conduit can be equippedwith active cooling capability, such as by provision of heat exchangeflow circuitry serving to reduce the temperature of the influent dopantgas entering the ionization chamber.

In the delivery of the isotopically-enriched, boron-containing compoundto the ion implanter tool, the isotopically-enriched, boron-containingcompound may be delivered, e.g., co-flowed to the ion implanter tool,with other component(s), such as inert gas species, e.g., argon, xenon,nitrogen, helium or the like, hydrogen, ammonia, other boron precursorssuch as natural abundance boron precursors, other isotopically-enrichedboron-containing precursors, other dopant precursors (i.e., non-borondopant precursors), or one or more of the foregoing components.

In one embodiment, the isotopically-enriched, boron-containing compound,e.g., enriched atomic mass 11 boron isotope-containing B₂F₄, isco-flowed to the ion implanter tool with an enriched atomic mass 11boron isotope-containing BF₃, whereby the dilution of theisotopically-enriched B₂F₄ with the isotopically-enriched BF₃ serves toenhance the resistance of the precursor stream to clogging of feed linesto the tool. In such case, the beam current can be maintained at levelsthat provide a significant benefit operationally, while concurrentlymaximizing the service life of the ion source.

In various other implementations of the use of isotopically-enriched,boron-containing precursors, operation of the ion implantation systemmay be carried out with in-situ cleaning of components of the system,such as by flow of a cleaning agent into the system or specificcomponents thereof to be cleaned, at periodic intervals. The cleaningagent utilized in such operation can be of any suitable type, such asfor example xenon difluoride, fluorine, nitrogen trifluoride, or otheragent that is effective in contact with deposits formed in the ionimplantation system or specific components thereof to be cleaned, to atleast partially remove such deposits. The location to be cleaned in theion implantation system by such periodic introduction of cleaning agentcan be the gas tube, the arc chamber, forelines, or any other locationsor regions in the tool or ancillary equipment in which deposits can beformed by chemical species utilized in the ion implantation operation.

In another implementation of the use of isotopically-enriched,boron-containing compounds as precursors, an ion implantation tool isoperated with isotopically-enriched atomic mass 11 boron B₂F₄ as theonly dopant precursor. In yet another implementation, ion implantationis carried out with isotopically-enriched atomic mass 11 boron B₂F₄ asthe dopant species on an ion implantation tool that also is used tocarry out doping operation involving a dopant precursor selected fromthe group consisting of arsine, phosphine, carbon dioxide, carbonmonoxide, silicon tetrafluoride, and boron trifluoride.

A further aspect of the disclosure relates to a gas storage anddispensing vessel comprising an isotopically-enriched, boron-containingcompound of any type as variously described herein. Such gas storage anddispensing vessel may for example contain an isotopically-enriched,boron-containing compound having the chemical formula of B₂F₄. The gasstorage and dispensing vessel in specific embodiments may comprise oneor more of a regulator, check valve, adsorbent, filter, and capillaryflow restriction device disposed in an interior volume of the vessel.The vessel in other embodiments may contain a storage medium for theboron-containing compound, such as a solid-phase physical adsorbent, oralternatively an ionic liquid storage medium. In still otherembodiments, the vessel can include a restrictive flow orifice locatedeither within an interior volume of the vessel or within a connectionport, e.g., outlet port, of the vessel.

Another aspect of the invention relates to a method of synthesizing anisotopically-enriched, boron-containing compound of any suitable type asdescribed herein above, comprising contacting a boron-containing gaswith a boron metal. In such method, one or both of the boron-containinggas and boron metal can be isotopically enriched. Thus, for example, thedisclosure contemplates a combination of isotopically enriched boronmetal and natural abundance boron trifluoride as being contacted, in oneembodiment. In another illustrative embodiment, the disclosurecontemplates combination of natural abundance boron metal andisotopically enriched boron trifluoride as being the contacted species,and in yet another illustrative embodiment, the disclosure contemplatescontacting of isotopically enriched boron metal and isotopicallyenriched boron trifluoride.

As a specific example of the synthesis method described above, theisotopically-enriched, boron-containing compound that is synthesized inthe contacting may be B₂F₄ and the boron-containing gas may be borontrifluoride.

The foregoing synthesis method may be carried out using atomic mass 10boron isotope in the boron metal at any suitable concentration. Inspecific embodiments, the concentration of atomic mass 10 boron isotopein the boron metal can be greater than 19.9%, 20%, 25%, 30%, 35%, 40%,45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9%, or 99.99%.

In other embodiments, the synthesis method may be carried out usingatomic mass 11 boron isotope in the boron metal, and in specificembodiments of such type, the concentration of atomic mass 11 boronisotope in the boron metal can be greater than 80.1%, 85%, 90%, 95%,99%, 99.9% or 99.99%.

In still other embodiments of the synthesis method, in which borontrifluoride is employed, isotopically enriched boron trifluoride speciescan be employed, such as boron trifluoride in which the concentration ofatomic mass 10 boron isotope is greater than 19.9%, 20%, 25%, 30%, 35%,40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9%, or99.99%.

In other embodiments, the synthesis method using boron trifluoride inisotopically enriched form can be carried out, in which the borontrifluoride is enriched in atomic mass 11 boron isotope, wherein theconcentration of atomic mass 11 boron isotope in the boron trifluorideis greater than 80.1%, 85%, 90%, 95%, 99%, 99.9% or 99.99%.

The disclosure in a further aspect relates to a method of improving beamcurrent for an ion implantation process, comprising use of anisotopically-enriched, boron-containing compound that is effective toproduce such improved beam current, in relation to a correspondingnon-isotopically-enriched, boron-containing compound. In a specificembodiment, the isotopically-enriched, boron-containing compoundcomprises isotopically-enriched B₂F₄.

A further aspect of the disclosure relates to a method of improving beamcurrent in an ion implantation process, comprising flowing anisotopically-enriched, boron-containing compound of any suitable type asdescribed hereinabove, and generating an ion beam from the compound. Insuch method, the isotopically-rich, boron-containing compound cancomprise a compound having a chemical formula of B₂F₄. Suchboron-containing compound upon ionization may form various ionic speciesand fragments, including one or more species from among B₂F₄ ⁺, B₂F₃ ⁺,B₂F₂ ⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, F⁺, B₂F₄ ⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺,BF₂ ⁺⁺, BF⁺⁺, B⁺⁺, F⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺, B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺,BF⁺⁺⁺, B⁺⁺⁺, and F⁺⁺⁺.

Significant improvement can be achieved in beam current as a result ofthe use of isotopically-enriched boron-containing compounds, and theircorrespondingly enriched boron-containing ionic species and fragments,as selected for implantation, by a selector comprising an AMU magnet orother selector. In such various embodiments, the concentration of atomicmass 11 boron isotope in the boron-containing compound, and in ionicspecies and fragments therefrom, can be greater than 80.1%, 85%, 90%,95%, 99%, 99.9% or 99.99%. Alternatively, boron-containing compoundsenriched in atomic mass 10 boron isotope can be utilized, i.e.,boron-containing compounds, and corresponding ionic species andfragments therefrom, in which the concentration of atomic mass 10 boronisotope is greater than 19.9%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%,60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9% or 99.99%.

In addition to utilizing isotopically-enriched compounds as feed gassources for ion implantation, the disclosure contemplates arrangementsin which combinations of boron-containing source compounds are utilized,to achieve various improvements, e.g., improvement in beam currentand/or other operating parameters of the ion implant operation,reduction in levels of decomposition and deposits therefrom, enhancementof resistance to clogging of flow passages in the ion implantationsystem, etc.

The disclosure further contemplates use of compounds that are homogenousin boron isotope as precursors for boron ion implantation, i.e.,boron-containing compounds, and ionic species and fragments therefrom,wherein all atomic boron is ¹⁰B or ¹¹B, to achieve improvements in beamcurrent or other operational parameters of the ion implantationoperation and system.

Use of isotopically-enriched boron-containing compounds has beendemonstrated to afford significant improvement in beam current forselected ionic species, e.g., beam current improvement levels of from 5to 30% or more, depending on the particular ionic species being selectedfor ion implantation. The ionic species, isotopically enriched in boroncontent, can be of any suitable type, and can for example include one ormore of B₂F₄ ⁺, B₂F₃ ⁺, B₂F₂ ⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, F⁺, B₂F₄ ⁺⁺, B₂F₃⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺, BF₂ ⁺⁺, BF⁺⁺, B⁺⁺, F⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺, B₂F₂⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺, BF⁺⁺⁺, B⁺⁺⁺, and F⁺⁺⁺. Thus, isotopic enrichmentcan be utilized to improve AMU magnet selection of ions of a desiredtype, such as for example BF₂ ⁺, BF⁺ or F⁺. By increasing the beamcurrent in the ion implant tool with such isotopically enriched species,it is possible to avoid the need for increasing the source gas flow andthe source arc power, such as may otherwise be required to achievehigher beam current levels, but which are less efficient and result inlow utilization of the source gas for ion implantation.

The use of isotopically-enriched B₂F₄ is particularly preferred, sincesuch boron source compound even at natural abundance isotopiccomposition affords significant improvement in beam current as comparedto beam currents obtained using boron trifluoride under the sameconditions and in the same ion implant tool, e.g., for species such asBF₂ ⁺ and B⁺. Isotopic enrichment can further increase the magnitude ofsuch improvements.

The disclosure in another aspect relates to generation of ion species inionization of an isotopically-enriched boron-containing compound, asuseful for ion implantation, in which the isotopically-enrichedboron-containing ion species is selected from among B₂F₄ ⁺, B₂F₃ ⁺, B₂F₂⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, F⁺, B₂F₄ ⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺, BF₂ ⁺⁺,BF⁺⁺, B⁺⁺, F⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺, B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺, BF⁺⁺⁺,B⁺⁺⁺, and F⁺⁺⁺. The disclosure further contemplates AMU magnet selectionof one or more of such ion species generated from ionization of anisotopically-enriched boron-containing compound, and implantation ofsuch isotopically-enriched boron-containing ion species in a substrate,such as a microelectronic device substrate.

The isotopically-enriched boron-containing species may be isotopicallyenriched to provide a concentration of atomic mass 11 boron isotope, ora concentration of atomic mass 10 boron isotope varied from naturalabundance levels, at any of the concentrations previously described,i.e., concentration of atomic mass 11 boron isotope in the ionic speciesgreater than 80.1%, 85%, 90%, 95%, 99%, 99.9% or 99.99%, or anisotopically-enriched boron containing species in which theconcentration of mass 10 boron isotope is greater than 19.9%, 20%, 25%,30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%,99.9% or 99.99%.

Another aspect of the present disclosure relates to a method of reducingthermal decomposition and deposition of material on surfaces of the ionimplantation tool as a result of using isotopically-enrichedboron-containing source compounds. Thermal decomposition ofboron-containing source compounds used in ion implantation can result indeposition of elemental boron with production of boron trifluoride orother byproduct gas species. Even if the gas feed line is sufficientlycooled, some thermal deposition inevitably occurs on the arc chamberwalls. The deposit formed as a result of such decomposition andassociated deposition can be a mixture of boron metal deriving from thesource gas, and tungsten or molybdenum from the arc chamber walls.Deposits can form in the gas feed lines near the ion source, as well asinside and on surfaces of nozzles, arc chamber base plates, and belowbase plate liners of the ionizer. Such deposits require periodicmaintenance removal, such as by abrasive cleaning and chemical methods,e.g., flow through the tool containing deposits of a suitable cleaninggas, to volatilize the deposits so that they can be removed. Theresulting effluent can be processed for remediation or recovery ofspecific materials from the effluent stream.

If the ion implanter is not dedicated to operation with only borondopants, various types of solid materials or ions may be formed byinteraction between the ions derived from the boron source compound andmaterials otherwise present in the vacuum chamber, depending on itsmaterials of construction, such as the tungsten and molybdenum materialspreviously described. In a tungsten arc chamber with aluminuminsulators, ions may be formed of widely varying type, including WF_(x)⁺ wherein x=0, 1, 2, 3, 4, 5 or 6 and AlF_(y) ⁺ wherein y=0, 1, 2, or 3.Such ions can react with the isotopically-enriched boron-containingsource compounds to form corresponding isotopically-enriched deposits.The isotopic character of such deposits may afford opportunity toutilize cleaning agents that are selective for same as a result of theirisotopic composition.

A further aspect of the disclosure relates to a method of preparing asource of the isotopically enriched, boron-containing compound of anysuitable type as described hereinabove, in which the method comprisesfilling a storage and dispensing vessel with the compound. In suchmethod, the isotopically enriched, boron-containing compound in oneembodiment has the chemical formula B₂F₄.

The isotopically-enriched, boron-containing compound of the presentdisclosure includes a wide variety of compounds, specific ones of whichare in gas, solid or liquid forms at standard conditions (1 atmpressure, 25° C.).

Thus, the disclosure contemplates an ionized composition useful for AMUseparation to generate ionic species for ion implantation, saidcomposition deriving from a boron precursor compound other than BF₃,wherein said boron precursor compound is isotopically enriched beyondnatural abundance in one of ¹⁰B and ¹¹B, and wherein said compositioncomprises one or more species from among B₂F₄ ⁺, B₂F₃ ⁺, B₂F₂ ⁺, BF₃ ⁺,BF₂ ⁺, BF⁺, B⁺, F⁺, B₂F₄ ⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺, BF₂ ⁺⁺, BF⁺⁺,B⁺⁺, F⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺, B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺, BF⁺⁺⁺, B⁺⁺⁺,and F⁺⁺⁺, the boron-containing ones of which are isotopically enrichedbeyond natural abundance in one of ¹⁰B and ¹¹B.

In such composition, the boron precursor compound can have the chemicalformula of B₂F₄ or any other suitable formula. The composition may beconstituted so that concentration of atomic mass 10 boron isotope in theboron-containing ionic species is greater than 19.9%, 20%, 25%, 30%,35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9%,or 99.99%. Alternatively, the composition may be constituted so thatconcentration of atomic mass 11 boron isotope in said boron-containingionic species is greater than 80.1%, 85%, 90%, 95%, 99%, 99.9% or99.99%.

A further aspect of the disclosure relates to a boron ionic speciesselected from among B₂F₄ ⁺, B₂F₃ ⁺, B₂F₂ ⁺, BF₃ ⁺, BF₂ ⁺, BF⁺, B⁺, B₂F₄⁺⁺, B₂F₃ ⁺⁺, B₂F₂ ⁺⁺, BF₃ ⁺⁺, BF₂ ⁺⁺, BF⁺⁺, B⁺⁺, B₂F₄ ⁺⁺⁺, B₂F₃ ⁺⁺⁺,B₂F₂ ⁺⁺⁺, BF₃ ⁺⁺⁺, BF₂ ⁺⁺⁺, BF⁺⁺⁺ and B⁺⁺⁺, and isotopically enrichedbeyond natural abundance in one of ¹⁰B and ¹¹B. In the boron ionicspecies, the concentration of atomic mass 10 boron isotope in said boronionic species is greater than 19.9%, 20%, 25%, 30%, 35%, 40%, 45%, 50%,55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9%, or 99.99%, oralternatively, the concentration of atomic mass 11 boron isotope in saidboron ionic species is greater than 80.1%, 85%, 90%, 95%, 99%, 99.9% or99.99%.

A still further aspect of the disclosure relates to a method ofimproving beam current for an ion implantation process, comprising useof an isotopically-enriched, boron-containing compound that is effectiveto form isotopically enriched ionic species producing such improved beamcurrent, in relation to a corresponding non-isotopically-enriched,boron-containing compound.

The isotopically-enriched, boron-containing compound may have thechemical formula of B₂F₄, or comprise any other suitableisotopically-enriched, boron-containing compound. In one embodiment, theconcentration of atomic mass 10 boron isotope in the isotopicallyenriched ionic species is greater than 19.9%, 20%, 25%, 30%, 35%, 40%,45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 99%, 99.9%, or 99.99%.In another embodiment, the concentration of atomic mass 11 boron isotopein said isotopically enriched ionic species is greater than 80.1%, 85%,90%, 95%, 99%, 99.9% or 99.99%.

A further aspect of the disclosure relates to use of diborane (B₂H₆) incombination with B₂F₄, as a dopant precursor composition. The B₂F₄ insuch dopant precursor composition may be isotopically-enriched asvariously described herein, or alternatively in anon-isotopically-enriched form. The diborane in such dopant precursorcomposition likewise may be isotopically enriched in boron isotopicspecies, or alternatively in a non-isotopically-enriched form. In theuse of such dopant precursor composition of B₂F₄ and diborane, the B₂F₄and diborane compounds can be premixed with one another and deliveredfrom a same source package, or alternatively, each of such B₂F₄ anddiborane compounds can be supplied from separate source packages, andflowed to the process tool from such separate source packages, in anysuitable manner. For example, the respective B₂F₄ and diborane compoundscan be co-flowed to the process tool from the separate source packages,or alternatively, such compounds may be delivered to the process tool ina sequential or alternating manner.

In another aspect of the disclosure, boron compounds and compositions ofthe present disclosure can be utilized for plasma doping of substratesfor production of solar cells, using boron ions derived from enriched,or non-enriched, B₂F₄ and B₂F₄-containing compositions variouslydescribed herein.

Referring now to the drawing, FIG. 1 is a schematic illustration of asemiconductor manufacturing facility including an ion implantationsystem arranged to receive an isotopically-enriched boron-containingprecursor from a precursor supply vessel, according to one embodiment ofthe present disclosure.

As shown in FIG. 1, the semiconductor manufacturing facility 180includes a dopant precursor supply vessel 182, arranged to dispensedopant precursor to the ion source chamber of the ion implantationsystem. The dopant precursor supply vessel 182 may be of any suitabletype, and may for example be constituted by an adsorbent-based fluidstorage and dispensing apparatus of the type commercially available fromATMI, Inc. (Danbury, Conn., USA) under the trademark “SDS”, arranged forsupplying dopant precursor gas at sub-atmospheric pressure, e.g., apressure below 600 torr, such as a pressure in a range of from about 10to about 500 torr, when the dopant precursor is of gaseous form andphysically adsorbable on the sorbent medium contained in the vessel.Alternatively, the dopant precursor may be of liquid form when stored ina pressurized state, e.g., in a pressure-regulated vessel of a typecommercially available from ATMI, Inc. (Danbury, Conn., USA) under thetrademark “VAC”, arranged to dispense gas at lower pressure from theliquid-containing vessel. As a still further alternative, the dopantprecursor may be of a solid form and may be provided in a vaporizervessel of a type commercially available from ATMI, Inc. (Danbury, Conn.,USA) under the trademark ProE-Vap, in which the dopant precursor solidis heated to generate precursor vapor for the ion implantationoperation.

The dopant precursor in the illustrative FIG. 1 system can for examplecomprise isotopically-enriched diboron tetrafluoride (B₂F₄), or anyother isotopically enriched boron-containing precursor.

The dopant gas is flowed in feed line 184 to gas delivery unit 186,which is constructed and arranged to suppress ionization of the dopantgas upstream of the high-voltage inlet 188 of ion source 190, in whichthe dopant gas is subjected to ionization to form dopant ions of thedesired character.

The resulting dopant ions are transmitted in passage 192 from the ionsource 190 to the implant chamber 194, in which a wafer (not shown) isdisposed in ion impingement position in relation to the ion stream ofthe dopant species.

The byproduct effluent from the implant chamber is flowed in effluenttreatment line 196 to effluent treatment unit 198, in which the effluentmay be subjected to treatment and/or reclamation processing, to producea final effluent that is discharged from the effluent treatment unit198.

While the invention has been has been described herein in reference tospecific aspects, features and illustrative embodiments of theinvention, it will be appreciated that the utility of the invention isnot thus limited, but rather extends to and encompasses numerous othervariations, modifications and alternative embodiments, as will suggestthemselves to those of ordinary skill in the field of the presentinvention, based on the disclosure herein. Correspondingly, theinvention as hereinafter claimed is intended to be broadly construed andinterpreted, as including all such variations, modifications andalternative embodiments, within its spirit and scope.

1. A boron-containing compound comprising two or more boron atoms and atleast one fluorine atom, wherein the compound contains a boron isotopein a concentration or ratio greater than a natural abundanceconcentration or ratio thereof.
 2. The compound of claim 1, containing(i) atomic mass 10 boron at concentration higher than 19.9% or (ii)atomic mass 11 boron at concentration higher than 80.1%.
 3. The compoundof claim 2, wherein the concentration of atomic mass 10 boron isotope isgreater than a value selected from the group consisting of 19.9%, 20%,25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%,96%, 97%, 98%, 99%, 99.9%, and 99.99%.
 4. The compound of claim 2,wherein the concentration of atomic mass 10 boron isotope is in a rangeselected from the group consisting of 20-25%, 25-30%, 30-35%, 35-40%,40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%, 80-85%,85-90%, 90-95%, 95-99% and 95-99.9%.
 5. The compound of claim 2, whereinthe concentration of atomic mass 11 boron isotope is greater than avalue selected from the group consisting of 80.1%, 85%, 90%, 95%, 96%,97%, 98%, 99%, 99.9% and 99.99%.
 6. The compound of claim 2, wherein theconcentration of atomic mass 11 boron isotope is in a range selectedfrom the group consisting of 81-85%, 85-90%, 90-95%, 95-99%, and95-99.9%.
 7. The compound of claim 1, wherein the compound contains twoboron atoms.
 8. The compound of claim 1, wherein the compound has achemical formula of B₂F₄.
 9. The compound of claim 1, having a ratio of¹¹B to ¹⁰B in a range of from 4.1 to 10,000.
 10. A method of implantingboron into a substrate, comprising: ionizing a boron-containing compoundcomprising two or more boron atoms and at least one fluorine atom,wherein the compound contains a boron isotope in a concentration orratio greater than a natural abundance concentration or ratio thereof,to generate boron ions; and implanting the boron ions into a substrate.11. The method of claim 10, wherein the boron-containing compoundcontains (i) atomic mass 10 boron at concentration higher than 19.9% or(ii) atomic mass 11 boron at concentration higher than 80.1%.
 12. Themethod of claim 11, wherein the concentration of atomic mass 10 boronisotope in the boron-containing compound is greater than a valueselected from the group consisting of 19.9%, 20%, 25%, 30%, 35%, 40%,45%, 50%, 55%, 60%, 65%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98%, 99%,99.9%, and 99.99%.
 13. The method of claim 11, wherein the concentrationof atomic mass 10 boron isotope in the boron-containing compound is in arange selected from the group consisting of 20-25%, 25-30%, 30-35%,35-40%, 40-45%, 45-50%, 50-55%, 55-60%, 60-65%, 65-70%, 70-75%, 75-80%,80-85%, 85-90%, 90-95%, 95-99% and 95-99.9%.
 14. The method of claim 11,wherein the concentration of atomic mass 11 boron isotope in theboron-containing compound is greater than a value selected from thegroup consisting of 80.1%, 85%, 90%, 95%, 96%, 97%, 98%, 99%, 99.9% and99.99%.
 15. The method of claim 11, wherein the concentration of atomicmass 11 boron isotope in the boron-containing compound is in a rangeselected from the group consisting of 81-85%, 85-90%, 90-95%, 95-99%,and 95-99.9%.
 16. The method of claim 10, wherein the boron-containingcompound contains two boron atoms.
 17. The method of claim 10, whereinthe boron-containing compound has a chemical formula of B₂F₄.
 18. Themethod of claim 10, wherein the boron-containing compound has a ratio of¹¹B to ¹⁰B in a range of from 4.1 to 10,000.
 19. The method of claim 10,wherein said ionizing is carried out in an ionization chamber and saidboron-containing compound is delivered through a conduit to theionization chamber for said ionizing, wherein the conduit is maintainedat a temperature effective to suppress clogging of the conduit and/ordecomposition of the compound in the conduit.
 20. The method of claim19, further comprising actively cooling at least one of the conduit andthe ionization chamber.